Britain's biggest selling daily newspaper, The Sun, is to start charging for its online content in the second half of 2013 as part of a radical shift in thinking about readers getting its journalism for free.

Mike Darcey, the chief executive of News International, said the parent company's current position – which allowed millions of readers to get the Sun's content for free – was "untenable".

The Sun online is read by about 30 million users every month – more than 10 times its 2.4m daily print circulation.

At an informal press event on Tuesday night, Darcey said "the second half of 2013 is a fairly safe bet" for the erection of a paywall. That would coincide with the launch of the publisher's new Premier League deal, allowing it to show clips of goals and match highlights .

The Daily Telegraph is also to charge for access to its website, becoming the first UK general interest national newspaper to use a metered paywall system.

Its publisher, Telegraph Media Group, will allow telegraph.co.uk users free access to 20 online articles a month. After that, readers will be charged £1.99 a month (or £20 a year) for access to further online content and to the Telegraph's smartphone apps.

It will also offer what it describes as a full digital pack, which also includes access to Daily Telegraph and Sunday Telegraph content on tablet devices plus loyalty club membership for £9.99 a month (or £99 per year).

With both packages, readers will be offered a one-month free trial before they are asked to commit to a subscription.

The metered model is favoured by newspapers across the US – notably the New York Times – and Canada. It is used in Britain by the Financial Times. By contrast, the Times and Sunday Times site is protected by a full paywall, restricting all access unless users pay for a subscription.The Telegraph's decision comes after its launch, in November, of the metered model on its international website. According to its press release for the UK launch, nine out of 10 people who take a month-long free trial go on to subscribe.

Existing print and digital subscribers in Britain will enjoy unlimited access to the website as part of their current package, at no extra cost.

The Telegraph's editor, Tony Gallagher, said: "We want to develop a closer rapport with our digital audience in the UK, and we intend to unveil a number of compelling digital products for our loyal subscribers in the months ahead."